Chapter 10.7, Problem 6E

(a)

Interpretation Introduction

Interpretation:Whether norbornene is chiral or not should be explained.

Concept introduction:Chiral carbon is any stereocenter attached to four different alkyl substituents. If any two of the substituent happen to be similar the center is regarded as achiral. However, the most essential criteria that help to distinguish a chiral or non-chiral system ispresence of any symmetry element. If any plane center or axis of symmetry is identified it makes molecule achiral and optically inactive.

Four kinds of symmetry elements that may be present are tabulated as follows:

  $\begin{array}{ccc}\text{S}\text{.No}& \text{Symmetry element}& \text{Notatio}n\\ 1.& \text{Axis of symmetry}& C_n\\ 2.& \text{Plane of symmetry}& \sigma \\ 3.& \begin{array}{l}\text{Alternating axis of }\\ \text{symmetry}\end{array}& S_n\\ 4.& \text{Center of symmetry}& i\end{array}$

The non-classical cation is unique carbocation that involves delocalization of electron density of filled bonding orbital over three carbons. It exists for systems such as phenonium ions,norbornyltosylate, brosylate, and nortricyclonium cations. They can be understood as carbocation that has transition state for two asymmetric equilibrium cation derived from anchimeric-assistance that represents neighboring group participation in the stabilization of positive charge as illustrated below.

  

(b)

Interpretation Introduction

Interpretation:Three chiral centers in $\text{exo-Norborneol}$ should be identified with asterisks.

Concept introduction:Chiral carbon is any stereocenter attached to four different alkyl substituents. If any two of the substituent happen to be similar the center is regarded as achiral. However, the most essential criteria that help to distinguish a chiral or non-chiral system ispresence of any symmetry element. If any plane center or axis of symmetry is identified it makes molecule achiral and optically inactive.

(c)

Interpretation Introduction

Interpretation: Chemical structure for the stereoisomer of $\text{exo}-\text{Norborneol}$ produced upon the hydration of norbornene along with its formation via norbornyl cation intermediate should be shown and whether this structure is a diastereomer or enantiomer of $\text{exo}-\text{Norborneol}$ should be identified.

Concept introduction: Chiral carbon is any stereocenter attached to four different alkyl substituents. If any two of the substituent happen to be similar the center is regarded as achiral. However, the most essential criteria that help to distinguish a chiral or non-chiral system isthe presence of any symmetry element. If any plane center or axis of symmetry is identified it makes molecule achiral and optically inactive.

The enantiomers are identical chemical compounds that have a mirror-image relationship to each other while diastereomers do not hold mirror image relationships.